Administering an injection is a process which presents a number of risks and challenges for users and healthcare professionals, both mental and physical.
Injection devices (i.e. devices capable of delivering medicaments from a medication container) typically fall into two categories—manual devices and auto-injectors.
In a manual device—the user must provide the mechanical energy to drive the fluid through the needle. This is typically done by some form of button/plunger that has to be continuously pressed by the user during the injection. There are numerous disadvantages to the user from this approach. If the user stops pressing the button/plunger then the injection will also stop. This means that the user can deliver an underdose if the device is not used properly (i.e. the plunger is not fully pressed to its end position). Injection forces may be too high for the user, in particular if the patient is elderly or has dexterity problems.
The extension of the button/plunger may be too great. Thus it can be inconvenient for the user to reach a fully extended button. The combination of injection force and button extension can cause trembling/shaking of the hand which in turn increases discomfort as the inserted needle moves.
Auto-injector devices aim to make self-administration of injected therapies easier for patients. Current therapies delivered by means of self-administered injections include drugs for diabetes (both insulin and newer GLP-1 class drugs), migraine, hormone therapies, anticoagulants etc.
Auto-injectors are devices which completely or partially replace activities involved in parenteral drug delivery from standard syringes. These activities may include removal of a protective syringe cap, insertion of a needle into a patient's skin, injection of the medicament, removal of the needle, shielding of the needle and preventing reuse of the device. This overcomes many of the disadvantages of manual devices. Injection forces/button extension, hand-shaking and the likelihood of delivering an incomplete dose are reduced. Triggering may be performed by numerous means, for example a trigger button or the action of the needle reaching its injection depth. In some devices the energy to deliver the fluid is provided by a spring.
US 2002/0095120 A1 discloses an automatic injection device which automatically injects a pre-measured quantity of fluid medicine when a tension spring is released. The tension spring moves an ampoule and the injection needle from a storage position to a deployed position when it is released. The content of the ampoule is thereafter expelled by the tension spring forcing a piston forward inside the ampoule. After the fluid medicine has been injected, torsion stored in the tension spring is released and the injection needle is automatically retracted back to its original storage position.
US 2007/0112310 A1 discloses an injector being automatic in that the needle is inserted into the injection site (e.g., a patient's skin) with user or caregiver assistance, the delivery is automatically initiated upon needle insertion, and the needle is retracted automatically after the end of delivery. Preferably the needle is not seen by the user prior to, during or after injection. Prior to and after injection, the needle is hidden in the device so as to avoid any potential injury or health risk to the user or health care provider. The injector includes a housing and a shield arranged to slide relative to the housing and a driver moving during drug delivery. The housing and shield form a cartridge enclosure. The cartridge is shielded and locked after delivery is completed. A needle-locking mechanism can be used in any number of pen-like injectors or safety needles.
U.S. Pat. No. 5,267,963 discloses an automatic injection device which, upon activation by the user, automatically extends a syringe with needle, delivers medication through the needle, and retracts the needle, thus keeping the needle hidden from view. All motions are achieved by means of a tension spring and a cam profile.
WO 2009/081103 A1 discloses an auto-injector for a syringe that is suitable for use in the injected delivery of drug to a patient. The auto-injector comprises a housing defining a housing cavity arranged for receipt of a syringe; and a needle delivery aperture through which a needle tip of the syringe protrudes during dispensing of the liquid drug formulation. The auto-injector further comprises a barrel coupling element that couples to the barrel of the syringe and is movable in tandem therewith; a syringe advancer for moving the syringe and barrel coupling element in tandem therewith from a rest position, in which the hollow needle, is within the housing to a use position, in which the needle tip protrudes through the needle delivery aperture; a syringe actuator for actuating the syringe by plunging said plunger within the barrel of the syringe to dispense the liquid drug formulation; a syringe retractor for retracting the syringe and barrel coupling element in tandem therewith from the use position to a retract position, in which the hollow needle is within the housing; and a syringe lock for locking the barrel coupling element and syringe coupled thereto in the retract position.
WO 2008/155377 discloses an inserter for an infusion set comprising an insertion needle and a spring unit assuring automatic insertion and automatic retraction of the insertion needle. The inserter for a medical device comprises—a housing,—a first body which is movable relative to the housing and comprising penetrating means pointing in the direction of insertion,—a second body which is also movable relative to the housing and—driving means which move respectively the first body and the second body relative to the housing wherein the driving means moves the first body in the direction of insertion and moves the second body in a direction different from the insertion direction.
DE 10 2005 038 933 A1 discloses an inserter for an infusion set comprising an insertion needle and a spring unit assuring automatic insertion and automatic retraction of the insertion needle. The inserter for a medical device comprises—a housing,—a first body which is movable relative to the housing and comprising penetrating means pointing in the direction of insertion,—a second body which is also movable relative to the housing and—driving means which move respectively the first body and the second body relative to the housing wherein the driving means moves the first body in the direction of insertion and moves the second body in a direction different from the insertion direction.